Plasma processing apparatus

Abstract

There is provided an inductively coupled plasma etching apparatus capable of suppressing a wavelength effect within a RF antenna and performing a plasma process uniformly in both a circumferential and a radial direction. In the plasma etching apparatus, a RF antenna 54 is provided on a dielectric window 52 to generate inductively coupled plasma. The RF antenna 54 includes an inner coil 58 , an intermediate coil 60 and an outer coil 62 in the radial direction. The inner coil 58 includes a single inner coil segment 59 or more than one inner coil segments 59 connected in series. The intermediate coil 60 includes two intermediate coil segments 61 ( 1 ) and 61 ( 2 ) separated in a circumferential direction and electrically connected with each other in parallel. The outer coil 62 includes three outer coil segments 63 ( 1 ), 63 ( 2 ) and 63 ( 3 ) separated in a circumferential direction and electrically connected with each other in parallel.

What is claimed is: 
     
       1. A plasma processing apparatus, comprising:
 a processing chamber having a dielectric window; 
 a substrate holding unit for holding thereon a processing target substrate within the processing chamber; 
 a processing gas supply unit configured to supply a processing gas into the processing chamber in order to perform a plasma process on the substrate; 
 a RF antenna provided outside the dielectric window in order to generate plasma of the processing gas within the processing chamber by inductive coupling; and 
 a high frequency power supply unit configured to supply a high frequency power having a frequency for generating a high frequency electric discharge of the processing gas, 
 wherein the RF antenna includes only three coils consisting of an inner coil, an intermediate coil and an outer coil with gaps therebetween in a radial direction, 
 the inner coil includes a single inner coil segment or more than one inner coil segments connected in series and disposed in a plane, 
 the intermediate coil includes a plurality of intermediate coil segments separated in a circumferential direction and electrically connected with each other in parallel and disposed in said plane, and 
 the outer coil includes a multiplicity of outer coil segments separated in a circumferential direction and electrically connected with each other in parallel and disposed in said plane, and 
 wherein a variable intermediate capacitor is electrically connected with the plurality of intermediate coil segments in series between a first node on the side of the high frequency power supply unit and a second node on a ground potential side, 
 a variable outer capacitor is electrically connected with the multiplicity of outer coil segments in series between the first and second nodes, 
 the numbers of the intermediate coil segments and the numbers of the outer coil segments are selected independently, and 
 connection conductors upwardly extending from the RF antenna are connected to each other in horizontal directions while spaced apart from the dielectric window at a predetermined distance to reduce electromagnetic influence upon the inner, intermediate and outer coils, 
 when high frequency power transmission lines are extended continuously from the first node to the second node, a winding direction of the intermediate coil on the high frequency power transmission line is opposite to winding directions of the inner coil and the outer coil on the high frequency power transmission lines in the circumferential direction, 
 the variable intermediate capacitor has an electrostatic capacitance having a range in which a combined reactance of the plurality of intermediate coil segments and the variable intermediate capacitor has a negative value, 
 an output side common capacitor between the second node and an earth line is electrically connected in series to the inner, intermediate and outer coil segments such that the variable intermediate capacitor, the variable outer capacitor and the output side common capacitor are directly connected to second node, and 
 the inner coil, the intermediate coil and the outer coil are electrically connected with each other in parallel between the first and second nodes. 
 
     
     
       2. The plasma processing apparatus of  claim 1 , wherein the inner coil segment is extended at least one round in a circumferential direction. 
     
     
       3. The plasma processing apparatus of  claim 1 , wherein a length of the inner coil segment is shorter than about ¼ of a wavelength of the high frequency power. 
     
     
       4. The plasma processing apparatus of  claim 1 , wherein the number of the outer coil segments is larger than the number of the intermediate coil segments. 
     
     
       5. The plasma processing apparatus of  claim 1 , wherein the outer coil segments are arranged so as to be extended along at least one round in the circumferential direction or along the most of the at least one round in the circumferential direction as a whole. 
     
     
       6. The plasma processing apparatus of  claim 1 , wherein a length of each outer coil segment is shorter than about ¼ of a wavelength of the high frequency power. 
     
     
       7. The plasma processing apparatus of  claim 1 , wherein the outer coil segments have the substantially same self-inductance. 
     
     
       8. The plasma processing apparatus of  claim 1 , wherein directions of electric currents flowing in the outer coil segments are the same in the circumferential direction. 
     
     
       9. The plasma processing apparatus of  claim 1 , wherein magnitudes of electric currents flowing in the outer coil segments are substantially same. 
     
     
       10. The plasma processing apparatus of  claim 1 , wherein the intermediate coil segments are arranged so as to be extended along at least one round in the circumferential direction or along the most of the at least one round in the circumferential direction as a whole. 
     
     
       11. The plasma processing apparatus of  claim 1 , wherein a length of each intermediate coil segment is shorter than about ¼ of a wavelength of the high frequency power. 
     
     
       12. The plasma processing apparatus of  claim 1 , wherein the intermediate coil segments have the substantially same self-inductance. 
     
     
       13. The plasma processing apparatus of  claim 1 , wherein directions of electric currents flowing in the intermediate coil segments are the same in the circumferential direction. 
     
     
       14. The plasma processing apparatus of  claim 1 , wherein magnitudes of electric currents flowing in the intermediate coil segments are substantially same. 
     
     
       15. The plasma processing apparatus of  claim 1 , wherein a direction of an electric current flowing in the inner coil, a direction of an electric current flowing in the intermediate coil and a direction of an electric current flowing in the outer coil are same in the circumferential direction. 
     
     
       16. The plasma processing apparatus of  claim 1 , wherein self-inductances of the inner, intermediate and outer coil segments are all substantially same. 
     
     
       17. The plasma processing apparatus of  claim 1 , wherein an electric current flowing in the intermediate coil segment is smaller than an electric current flowing in each inner coil segment and each outer coil segment. 
     
     
       18. The plasma processing apparatus of  claim 1 , wherein the variable outer capacitor has an electrostatic capacitance having a range in which a combined reactance of the multiplicity of outer coil segments and the variable outer capacitor has a positive value. 
     
     
       19. The plasma processing apparatus of  claim 1 , wherein the number of the intermediate coil is plural, and the intermediate coils are electrically connected with each other in parallel between the inner coil and the outer coil. 
     
     
       20. The plasma processing apparatus of  claim 1 , wherein the intermediate coil is wound one round and at least one of the inner coil and the outer coil is wound multiple rounds. 
     
     
       21. The plasma processing apparatus of  claim 1 , wherein the high frequency power supply unit includes:
 a high frequency power supply configured to supply the high frequency power; 
 a matching unit for matching impedance on the side of the high frequency power supply and impedance on a load side; and 
 a transformer having a primary coil electrically connected with an output terminal of the matching unit and a secondary coil electrically connected with the RF antenna. 
 
     
     
       22. The plasma processing apparatus of  claim 1 , wherein the dielectric window constitutes all or a part of a ceiling plate of the processing chamber, and
 the inner coil, the intermediate coil and the outer coil are provided on the dielectric window. 
 
     
     
       23. The plasma processing apparatus of  claim 1 , wherein the inner coil, intermediate coil and the outer coil are coaxially arranged. 
     
     
       24. The plasma processing apparatus of  claim 1 , wherein at least one inner gap formed at the inner coil, at least two intermediate gaps formed at the intermediate coil and at least two outer gaps formed at the outer coil are arranged so as not to have same azimuth angles.